This disclosure generally relates to position or location approaches in GSM, CDMA, and UMTS networks. Further, this disclosure relates to user and control plane location approaches in core networks and GERAN, UTRAN, and Complementary Access radio access networks.
Mobile communications infrastructure is typically conceptualized in two generally separate components: the core network (CN); and the radio access network (RAN). Together, this infrastructure enables user equipment (UE), the RAN, and CN to be developed and implemented separately according to the permissive standards set by organizations such as 3GPP and ITU. Thus, various types of RANs, such as GERAN or UTRAN, can be paired with a single UMTS CN. Also, the UMTS standards provide for protocol separation between data related to user communications and data related to control of the network's various components. For example, within a UMTS mobile communications network, User Plane (UP) bearers are responsible for the transfer of user data, including but not limited to voice or application data. Control Plane (CoP) bearers handle control signaling and overall resource management.
As mobile networks transition towards 3G and beyond, location services (LCS, applications of which are sometimes referred to as Location Based Services, or LBS) have emerged as a vital service component enabled or provided by wireless communications networks. In addition to providing services conforming to government regulations such as wireless E911, LCS solutions also provide enhanced usability for mobile subscribers and revenue opportunities for network operators and service providers alike.
Position includes geographic coordinates, relative position, and derivatives such as velocity and acceleration. Although the term “position” is sometimes used to denote geographical position of an end-user while “location” is used to refer to the location within the network structure, these terms may often be used interchangeably without causing confusion. Common position measurement types used in mobile positioning or LCS include, but are not limited to, range, proximity, signal strength (such as path loss models or signal strength maps), round trip time, time of arrival, and angle of arrival. Multiple measurements can be combined, sometimes depending on which measurement types are available, to measure position. These combination approaches include, but are not limited to, radial (for example, employing multiple range measurements to solve for best agreement among circular loci), angle (for example, combining range and bearing using signal strength or round trip time), hyperbolic (for example, using multiple time-of-arrival), and real time differencing (for example, determining actual clock offsets between base stations).
Generally, LCS methods are accomplished through CoP or UP methods. CoP Location (CoPL) refers to using control signaling within the network to provide location information of the subscriber or UE. UP Location (UPL), such as Secure User Plane Location (SUPL) uses user data to provide location information. CoPL location approaches include, but are not limited to, Angle-of-Arrival (AoA), Observed Time-Difference-of-Arrival (OTDoA), Observed-Time-Difference (OTD), Enhanced-OTD (E-OTD), Assisted Global Positioning System (A-GPS), and Assisted Galileo Navigation Satellite System (A-GNSS). UPL approaches include, but are not limited to, Assisted Global Positioning System (A-GPS), and Assisted Galileo Navigation Satellite System (A-GNSS), where this position data is communicated over Internet Protocol (IP).
There are two established architectures associated with location determination in modern cellular networks. They are Control Plane (CoP) and User Plane (UP) architectures. Typically location requests are sent to a network through a query gateway function 1. Depending on the network implementation CoP 15 or UP 10 may be used but not a combination of both, as shown in FIG. 1. Note that queries may also come directly from the target device itself rather than via a gateway. Similarly, CoP or UP may be used but not both.
The difference between user plane and control plane, strictly, is that the former uses the communication bearer established with the device in order to communicate measurements. The latter uses the native signaling channels supported by the controlling network elements of the core and access to communicate measurements. As such, CoPL supports AGPS—it uses control plane signaling interfaces to communicate GPS data to/from the handset. Similarly UPL can do EOTD—the handset takes the timing measurements but it communicates them to the location platform using the data bearer.
UPL has the advantage of not depending on specific access technology to communicate measurement information. CoPL has the advantage that it can access and communicate measurements which may not be available to the device. Current models require network operators to deploy one or the other; CoPL or UPL
Control Plane Location (CoPL) uses the native signaling plane of the network to establish sessions and communicate messages associated with location requests and to communicate measurements used for determining location. The control plane is the signaling infrastructure used for procedures such as call control, hand-off, registration, and authentication in a mobile network; CoPL uses this same infrastructure for the performing location procedures. CoPL can utilize measurements made by both the control plane network elements as well as the end-user device being located.
FIG. 2A illustrates an exemplary architectural diagram of CoPL. The mobile station or mobile appliance 101 communication with the base transceiver station (BTS) 105 via wireless interface Um. The base station controller (BCS)107 manages radio resources including the BTS 105 via the Abis interface. The Abis interface is an open interface completely defined as part of the ETSI specification for GSM and carries the call set up information, including voice channel assignments between the BSC 107 and BTS 105. The Mobile switching center/visitor's location register (MSC/VLR) 113 coordinates between the mobile appliance communication network and the global mobile location center (GMLC) 117.
In operation, a location measurement device (not shown) may be connected to the BSC 107 via the Abis wire line interface and makes measurements on the RF signals of the Um interface, along with other measurements to support one or more of the position methods associated with the CoPL. The measurements from the location measurement units are sent to a servicing mobile location center (SMLC) 109 via BCS 107 where the location of MS 101 can be determined. The BTS 105, BSC 107 and SMLC 109 form a base station subsystem (BSS) 103.
The GMLC 117 is connected to the home location register (HLR)111 over an Lh interface and the MSC/VLR 113 over an Lg interface. The global mobile switching center (GMSC)115 is operably connected to the MSC/VLR 113.
The operation of a CoPL architecture is shown in FIG. 2B. This shows the 3GPP location services architecture. The gateway mobile location centre (GMLC) 117 is the network element that receives the location requests. The GMLC queries the HLR 111 over the Lh interface to find out which part of the access network 107 the target device is currently being served by. The GMLC 117 sends a location request to the current serving core network node 113 via the Lg interface. The current serving core network node 113 (e.g. MSC or serving GPRS service node (SGSN)) then passes the request to the part of the access network 107 that the target device is attached to z(a GERAN BSC or UTRAN RNC for example). This access network element 107 then invokes the facilities of the SMLC 109. The location request session between the access network node 107 and the SMLC 109 provides a channel by which the SMLC 109 can ask for network measurements or to send messages to the end-user device 101 so that device measurement information can be exchanged. The SMLC 109 may also obtain location measurement information from external devices 110 such as location measurement units (LMUs) which take RF readings from the air interface for example. Similarly, the device may also take measurements from external systems, such as GPS satellites, and communicate these to the SMLC 109.
Developed as an alternative to CoPL, Secure User Plane Location (SUPL) is set of standards managed by the Open Mobile Alliance (OMA) to transfer assistance data and positioning data over IP to aid network and terminal-based positioning technologies in ascertaining the position of a SUPL Enabled Terminal (SET).
User Plane Location (UPL) does not explicitly utilize the control plane infrastructure. Instead it assumes that a data bearer plane is available between the location platform and the end-user device. That is, a control plane infrastructure may have been involved in establishing the data bearer so that communication can occur with the device but no location-specific procedural signaling occurs over the control plane. As such UPL is limited to obtaining measurements directly from the end-user device itself.
SUPL includes a Location User Plan (Lup) reference point, the interface between the SUPL Location Platform (SLP) and SET, as well as security, authentication, authorization, charging functions, roaming, and privacy functions. For determining position, SUPL generally implements A-GPS, A-GNSS, or similar technology to communicate location data to a designated network node over Internet Protocol (IP).
FIG. 3A illustrates an exemplary architectural diagram for SUPL. The illustrated entities represent a group of functions, and not necessarily separate physical devices. In the SUPL architecture, a SUPL Location Platform (SLP) 201 and SUPL-enabled terminal (SET) 207 are provided. The SLP 201 generally includes a SUPL Location Center (SLC) 203 and a SUPL Positioning Center (SPC) 205. The SLC and SPC optionally communicate over the L1p interface, for instance, when the SLC and SPC are deployed as separate entities. The SET 207 generally includes a mobile location services (MLS) application, an application which requests and consumes location information, or a SUPL Agent, a service access point which accesses the network resources to obtain location information.
For any SET, a SLP 201 can perform the role of the home SLP (H-SLP), visited SLP (V-SLP) or emergency SLP (E-SLP). An H-SLP for a SET includes the subscription, authentication, and privacy related data for the SET and is generally associated with a part of the SET's home PLMN. A V-SLP for a SET is an SLP selected by an H-SLP or E-SLP to assist positioning. An E-SLP for a SET is an SLP associated with or contained in the PLMN serving the SET. The E-SLP may performs positioning in association with emergency services initiated by the SET.
The SLC 203 coordinates operations of SUPL in the network and interacts with the SET over the User Plane bearer to perform various functions including, but not limited to, privacy, initiation, security, roaming, charging, service management, and positioning calculation. The SPC 205 supports various functions including, but not limited to, security, assistance delivery, reference retrieval, and positioning calculation.
SUPL session initiation is network-initiated or SET-initiated. The SUPL architecture provides various alternatives for initiating and facilitating SUPL functions. For example, a SUPL Initiation Function (SIF) is optionally initiated using a Wireless Application Protocol Push Proxy Gateway (WAP PPG) 211, a Short Message Service Center (SMSC/MC) 213, or a User Datagram Protocol/Internet Protocol (UDP/IP) 215 core, which form user plane bearer 220.
The operation of UPL is shown in FIG. 3B. Secure User Plane Location is a standard specification for UPL. Location requests come to the SLP 201 from external applications or from the end-user device itself. If a data session does not exist between the SLP 201 and the device 207 already, then the SLP 201 may initiate a request such that an IP session (user plane bearer 220) is established between the device 207 and the SLP 201. From then on, the SLP 201 may request measurement information from the device 207. It device may also take measurements from the network 107 or from external systems such as GPS 210. Because there is no control plane connectivity to the network, the SLP 201 cannot directly request any measurement information from the network 107 itself.
More information on SUPL, including the Secure User Plane Location Architecture documentation (OMA-AD-SUPL), can be readily obtained through OMA.
User Plane location, especially after the development of SUPL standards, is generally thought to provide an affordable and rapid upgrade path to provide LCS for mobile network operators currently without an CoPL solution. However, UPL (including SUPL) suffers from several drawbacks compared to CoPL.
A standard user-plane location architecture has to be applied to all location requests for a given location based service because there is no a-priori knowledge of which part of the network the device is being served by, nor what the location capabilities of the device are. User-plane signaling has to be invoked every time and, in many scenarios, may fail completely if the network or device are not compatible with this architecture.
When a pure user-plane approach is used, there is no ability to request network measurement information from the radio controllers used by the network. This additional information, which can be useful as an alternative or to augment the measurements obtained from the device, is not accessible. This compromises in terms of the location system's ability to provide optimal results.
A significant motivator for SUPL were the significant dependencies on the vendors for access equipment, specifically the radio access controllers, to support consistent standards behavior. There is also a dependency on core network signaling for consistent LCS service. However, the issue of consistent implementation of the MAP signaling has not been found to be significant.
Further, the basic LCS functionality at the BSS 103 has become increasingly commoditized. For instance, basic Lb interface and PLR messaging are nearly universally supported across access vendors.
Current definitions of SUPL (per the OMA) decouple the end-to-end signaling from the control plane. This bypasses much of the value-add that the core control-plane offers. Such offerings include, but are not limited to, native access-network emergency service application support, privacy checking against subscriber profile in the HLR, ability to support LCS requests from roaming partners' GMLCs. In addition, the lowest common denominator functionality of the access control-plane (Lb interface functions) is lost. These lost abilities include, but are not limited to, getting a rapid enhanced-cell fix with TA/NMR measurements, performing multiple TA requests to augment network measurement information, obtaining network measurements (e.g. UTDOA request) not available from a SET.
Further, UPL does not associate position information with a voice call from a user. Accordingly, UPL approaches are not used for certain emergency services, such as e911 in which the physical location directly associated with an emergency communication must be automatically ascertained.
Much of the benefits of control-plane functionality, therefore, is sacrificed with the wholesale adoption of a user-plane approach.
Therefore, regulatory requirements and evolving commercial demands illustrate the disadvantages of a CoPL-only or SUPL-only network architecture.